Acceptor conjugation extension engineering in donor–acceptor covalent organic frameworks for efficient H2O2 photoproduction

Abstract

Developing efficient photocatalysts for solar-driven hydrogen peroxide (H₂O₂) production is highly desirable. Herein, we report the rational design of a series of donor–acceptor covalent organic framework (COF) photocatalysts (Ph-Py-COF, BT-Py-COF, and NT-Py-COF) via a conjugation extension strategy to boost photocatalytic H₂O₂ production. These isostructural COFs were constructed using a pyrene-based donor and three different acceptors with systematically varied electron-withdrawing capabilities and conjugation lengths, including benzene, benzothiadiazole (BT), and its π-extended derivative, naphthothiadiazole (NT). Systematic investigations reveal that extending the conjugation of the acceptor unit progressively enhances the optoelectronic properties of the COFs. Among them, NT-Py-COF, incorporating the strongest and most conjugated NT acceptor, demonstrates the most effective promotion of charge separation and transport, as evidenced by experimental and theoretical results. Consequently, NT-Py-COF achieves a superior photocatalytic H₂O₂ production rate of 2546.1 μmol g⁻¹ h⁻¹, significantly outperforming its counterparts. This work underscores the conjugation extension strategy as a powerful and versatile approach for developing high-performance COF photocatalysts for solar-to-chemical energy conversion.